From FAQs on the site
I can’t enter my code.
The codes are made up of letters only, so please double check that you are not entering any numbers. For example, the number 1 could be mistaken for the letter l, or the number 0 for the letter O.
I bought some Kellogg’s cereal to take part in the offer but it does not have a unique code inside the box, what do I do?
Please check that you have a promotional pack by checking if the promotional message “Free TIP n’ SIP Bowl” is on the front. If your pack is a promotional pack, you should be able to find the unique code on the inside front panel. The code is not printed on the outside of the pack. If you still cannot find the code, please contact the Kellogg’s Careline, on 0800 626 066 (UK) & 1800 626 066 (ROI) between 9:00am and 5:00pm, Monday to Friday, excluding Bank Holidays. Alternatively, you can email us via the Kellogg’s website at www.kelloggs.co.uk/promotions (UK) or www.kelloggs.ie/promotions (ROI).