At home it was food packaging that i found hardest. Our grey waste has halved over the last couple of years and recycle gone up - but still waste. Each meal I made seemed to have some food wrapper or container that although often minimised was still there. I realise there is an balance between food waste / preservation verses wrapping - but certainly one to focus on for us.
On holiday is was plastics. Water by default always came in bottles - masses of them. We tried where possible to use the water feature of the soda drinks machine to fill our normal bottles , plus a few disposable ones, but got very funny looks from the staff. Water purity was an issue but it was also seen as "polite" for staff to keep providing bottles each time.
Plastic glasses were the other issue as glass was not allowed in outside areas for HSE around pools etc. Culture was a new plastic cup each time - we put our names on ours and tried to reuse, but every time not looking they were kindly cleared away and replaced with new. Answer was to kindly always decline and then go get any drinks yourself forcing the re-use of plastics. Small wins and many strange looks