Step 1 want or need people want straws so that they do not have to put there mouth on the class or the can
Step2 Design brief and constrant original design could have been a piece of bamboo the problems with thatg 1 it would be hard to mass produce that having to bang holes throug the bamboo 2 If someone chewed on it it would splinter and they could choke or end up with a mouth full of wood shards maybe then a metal straw metal is much better for the environment and you could use one again and again but for the manufacturers it would be too expensive to mass produce and would be to heavy so plastic would work best it is cheep for the manufacturers to make and is light weight
Step 3 must be straight must be made of plastic must be bigger than a regular glass
Step 4 you might want to bend your straw but if you do it blocks the liquid so you could put a bend in the straw by making an extendibal joint this means that you could have it strate if you wanted to on at an angle
Step 6 some design floors may include the joint being week and it braking and then leaking.
Step 7 and 8 I think this is the best design