Kitchen window covering or curtains
Easy answer is either throw a sheet or blanket or fabric over a pole or wire or use clips for the job, available from haberdashery dept.
To best answer your question it would be helpful to know if you desire window coverings that:
-insulate from hot sun or winter cold air
-block bright sunlight
-give privacy during the day, or just at night
-can be easily opened and closed
-can be easily washed
Please post a picture of your window so that we can also see what type of space you have to mount window covering hardware.
If you are an experienced home sewer with a machine, I doubt you would be asking. As for simple curtains, you just make a casing and hem it. However if you are not experienced visit a large thrift shop like a Goodwill store, or Salvation Army Thrift store (sometimes church sales)- they have tons of curtains panels for a lot less than buying fabric and matching thread. Discount stores also sell them inexpensively. Also consider a vinyl window shade cut to fit.
A tension rod can also be used with a decorative piece of fabric or table cloth for a super easy option! I hope this helps!