def cut_everything(sentence, max_length):
    """
    reduces each word in sentence to a length of 4

    :type sentence: string
    :param sentence: the sentence to cut
    :type max_length: int
    :param max_length: the length to which the sentence will be reduced
    """
    words = sentence.split()
    for index, word in enumerate(words):
        word_length = len(word)
        if word_length > 4:
            to_cut = len(sentence) - max_length
            to_keep = word_length - to_cut
            if to_keep < 4:
                to_keep = 4
            words[index] = word[:to_keep]
            sentence = ' '.join(words)
            if len(sentence) <= max_length:
                break

    return sentence

MAX_WORD_LENGHT = 4

to_keep = word_length - to_cut
if to_keep < 4:
to_keep = 4

to_keep = max(word_length - to_cut, 4)

import doctest

MAX_WORD_LENGHT = 4

def cut_everything(sentence, max_length):
    """
    reduces each word in sentence to a length of 4

    :type sentence: string
    :param sentence: the sentence to cut
    :type max_length: int
    :param max_length: the length to which the sentence will be reduced

    >>> cut_everything('foo bar foooobar', 16)
    'foo bar foooobar'

    >>> cut_everything('foo bar foooobar', 8)
    'foo bar fooo'

    >>> cut_everything('foo bar foooobar baaarfoo', 20)
    'foo bar fooo baaarfo'

    >>> cut_everything('fooooooo baaaaaaar foooobar baaarfoo', 2)
    'fooo baaa fooo baaa'
    """
    words = sentence.split()
    chars_to_cut = len(sentence) - max_length
    for index, word in enumerate(words):
        word_length = len(word)
        if chars_to_cut > 0 and word_length > MAX_WORD_LENGHT:
            to_keep = max(word_length - chars_to_cut, MAX_WORD_LENGHT)
            words[index] = word[:to_keep]
            chars_to_cut -= word_length - to_keep
    return ' '.join(words)

if __name__ == '__main__':
    doctest.testmod()