Tips for Fixing H&M clothes ?

I like to shop at stores like Zara, H&M, Stradivarius,etc. because of their lower price point. However, their clothes are more affordable because they are often lacking in terms of quality construction . Is there a sewing hack to strengthen the seams on a garment that is already made by one of these stores? Something that isn't to hard to do? Thanks in advance for your advice.