Aluminium is fine for acidic beverages and it is possible to buy juice in a can, but that would be a single serving. Juice and milk make sense to buy in larger sizes for multiple servings. Plastic bottles are also an option for those, but it really depends on how they’re recycled locally if that makes more sense than the cartons.
The aluminium red solo cups ought to be recyclable just as any other aluminium product, provided that they’re returned in the first place and not mixed with other disposable garbage. Selling them as disposable seems counterproductive. A better option would be to use actual cups or glasses for picnics and bring them back home. Washing a cup in a dishwasher is much better than recycling aluminium.
It’s not easy for consumers to make a good choice.