In the past I've given food and drinks, but often they have then pushed for money as well, which makes me think they're probably not homeless, but are begging to feed their drug habit. I'm not judging them, but I don't want to fund their lifestyle choice
Recently I was in town one evening and a distressed young woman was asking passers by for help. She was in tears and looked distraught. I asked what was wrong and she said she'd had her purse stolen and had no money to get the bus home. I started to reach into my bag for my purse but as I did so an older woman quickly whispered in my ear "Don't - it's a scam - she's always here!" At that point the scammer turned really nasty, said the woman was a "lying, fucking bitch!" and looked like she was going to hit her. I gave the scammer some change just to stop her getting more aggressive, but felt such a fool. She could have got an Oscar for her acting though - very convincing.
In December I decided to find some genuinely homeless people and give them some gift bags, containing warm socks, food and drink, plus maybe some toiletries and chocolate, just to make sleeping rough a bit more bearable at Christmas. I bought the items and began seeking out the homeless by walking around shopping precincts after the shops closed. I felt sure I would find them sleeping in shop doorways, etc, near the places they beg during the day. There were none to be found. It made me feel quite cynical. I have given the items to a food bank.
I totally understand why people don't want to interact with beggars, whether they're homeless or not, because in shopping centres it's actually pretty normal to walk past strangers without saying hello or making any eye contact, and in the case of beggars, so many of them have an agenda that is nothing to do with being homeless. Also, a smile and hello to a beggar is pretty patronising, unless that is what you do to every stranger you pass, because it's like you think they are so pitiful their day will be brightened up by the crumbs of your attention. Truth be told, most of them would probably prefer you fling some cash in their pot without a word or a glance, rather than bestow a pitying smile on them - they're not begging for your company and probably won't welcome your pity.
Give money or don't - but feel no guilt, either way, because you didn't cause their problems.