UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): September 10, 2026

BYNORDIC ACQUISITION CORPORATION

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: +46 707 29 41

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 or Rule 12b-2 of the Securities Exchange Act of 1934.

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01 Entry into a Material Definitive Agreement.

On September 11, 2026, byNordic Acquisition Corporation (“BYNO”, the “Company”) issued a promissory note (the “Note”) in the principal amount of up to $150,000 to Thomas L. Fairfield (the “Lender”), the Chief Operating Officer and Chief Financial Officer of the Company. The initial advance under the Note was $8,850.20. The proceeds of the Note will be used to provide the Company with general working capital, including funds to make deposits required in connection with extensions of the Company’s business combination period.

The Note bears no interest and is payable in full upon the earlier to occur of (i) consummation of the Company’s initial business combination (the “Maturity Date”), or (ii) the 180^th day following the dissolution of the Company, as such date may be extended by the Lender. A failure to pay the principal on the Maturity Date shall be deemed an event of default, in which case the Note may be accelerated. If the Company does not consummate an initial business combination, the Note will be repaid solely to the extent the Company has funds available outside its trust account established in connection with the Company’s initial public offering.

A copy of the Note is attached as Exhibit 10.1 to this Current Report on Form 8-K and is incorporated herein by reference. The disclosures set forth in this Item 1.01 are intended to be summaries only and are qualified in their entirety by reference to the Note.

Item 2.03 Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant.

The disclosure contained in Item 1.01 of this Current Report on Form 8-K is incorporated by reference in this Item 2.03.

Item 8.01. Other Events.

Extension of Business Combination Period to October 12, 2026

As previously disclosed, on August 6, 2026, BYNO held an annual meeting of stockholders to consider, among other things, proposals to amend BYNO’s amended and restated certificate of incorporation in order to extend the time BYNO has to complete its initial business combination from August 12, 2026 to August 12, 2027, or such earlier date as determined by the Company’s board of directors (the “Board”), in its sole discretion, and to allow BYNO, without another stockholder vote, to elect to extend the termination date by one additional month, for a total of twelve additional months, until August 12, 2027, unless the closing of BYNO’s initial business combination shall have occurred prior thereto.

On September 11, 2026, an officer of the Company funded the extension that had previously been approved by the Board by depositing $8,850.20 into the Trust Account, thereby extending the time available to the Company to consummate its initial business combination from September 12, 2026 to October 12, 2026.

BYNO issued the press release distributed herewith on September 14, 2026. The materials attached as Exhibit 99.1 are incorporated by reference herein.

Forward-Looking Statements

This Current Report on Form 8-K includes “forward-looking statements” within the meaning of the safe harbor provisions of the United States Private Securities Litigation Reform Act of 1995. Certain of these forward-looking statements can be identified by the use of words such as “believes,” “expects,” “intends,” “plans,” “estimates,” “assumes,” “may,” “should,” “will,” “seeks,” or other similar expressions. Such statements may include, but are not limited to, the Company’s cash position and cash held in the Trust Account and any proposed remediation measures with respect to identified material weaknesses. These statements are based on current expectations on the date of this Current Report on Form 8-K and involve a number of risks and uncertainties that may cause actual results to differ significantly. The Company does not assume any obligation to update or revise any such forward-looking statements, whether as the result of new developments or otherwise. Readers are cautioned not to put undue reliance on forward-looking statements.

Item 9.01. Financial Statements and Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.