Poor you, it’s awful. If you are in pain you should prob see a healthcare professional….
Water is the best short term, to flush out your bladder, if it’s serious that won’t do it though.
Pharmacists in Spain/France/Italy/Greece have more power than in the UK and can give you antibiotic sachets if you ask nicely, at their discretion. Only do this if you have taken them before and can compare the contents of the UK brand to the ones they have, so you have no adverse reactions! In Spain the brand name is Monurol for example.
if you are in the EU and you bagged yourself a free blue emergency insurance card for emergencies before Brexit that is still valid you can call the non-emergency line, like 111 here, or speak to a local pharmacist and they can usually put you in touch with an English speaking doctor for no fee who can prescribe it.
If you have travel health insurance of any kind they can do the same, you might have to pay cash for the appointment and prescription first then get it reimbursed after, make sure the doctor acknowledges that on the receipt. One-off private gp or gyno fees range around €100, might be worth it.
If you are not in Europe, call the local consulate, it’s free and they are usually happy to help. They have heard and seen it all so don’t be embarrassed.
Also bicarbonate is not so used on the continent as baking styles are different, you might find it in the cleaning section or at a pharmacy, but check it’s ok for ingestion not just scrubbing.
Enjoy your holiday and ask your husband for help! Don’t leave it until the weekend.
Sorry that was a lot. I’ve wet my pants from cystitis, have since learnt to spot the very early symptoms and to drink water like I drink wine, so the patronising advice is lovingly given!